Method of and apparatus for fault location on electrical conductors.



No. 859,556. PATENTED JULY 9, 1907 H. M. FRIENDLY. METHOD OF ANDAPPARATUS FOR FAULT LOCATION ON ELECTRICAL GONDUGTORS.

APPLIOATION FILED APR.10,1905.

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HMFh'endz v A fwenZ or? gmaz yWM 6M H. M. FRIENDLY. METHOD OF ANDAPPARATUS FOR FAULT LOCATION ON ELECTRICAL CONDUCTORS.

APPLICATION FILED APR. 10. 1905.

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I HMRiendl wilmsses. fiwenfim W A @Mmm' PATENTED JULY 9, 1907.

UNITED STA S PATENT OFFICE.

HERBERT M. FRIENDLY, OF PORTLAND, OREGON.

METHOD OF AND APPARATUS FOR FAULT LOCATION ON ELECTRICAL CONDUCTORS.

Specification of Letters Patent.

Patented July 9, 1907.

Application filed April 10, 1905. Serial No. 264,899.

To all whom it may concern:

lie it known that I, HERBERT M. FRIENDLY, a citizen of the United Statesof America, and a resident of Portland, county of Multnomah, and Stateof Oregon, have invented a new and useful Improvement in Methods of andApparatus for Fault Location on Electrical Conductors, oi which thefollowing is a specification.

My invention relates -to that class of electrical testing devicesintended for use in locating grounds or crosses on electrical conductorsin cables or on insulators, and involving the use of adjustableresistances and of a galvanometer or other current-detecting dcvico.

It is well known to utilize adjustable resistances and galvanometors orother current detectors, in connection with sources of current forlocating grounds and crosses upon lines; but in all the methods whichare available for use with apparatus of limited complication andreasonable scope, a certain amount of mathematical calculation isnecessary after the manipulation of the instruments has been completed.For the reason that such calculations are necessary and because theyinvolve the use of mathematical processes not familiar to all persons,fault location is an art which has 'relmtined relatively unknown to manypersons whose occupation otherwise would adapt them to conduct suchundertakings.

My invention enables fault locations to be made with a minimum ofoperations and calculations, rend er- .ing possible the formulation ofspecific instructions which need but to be followed by a person of usualintelligence and limited special training to enable the results to bereached in terms commonly understood and not complex.

My invention is illustrated in the accompanying drawings, in which,

Figure 1 shows a plan view of the commutator or master-switch, togetherwith a diagrammatic arrangement of the other elements associated withsaid commutat'or in one form of a complete testing set made in Similarcharacters refer to similar parts throughout the several views. i

In Fig. 1 are contained the elements of'illustration required to makeclear the construction of the commutator of my invention, this being adevice of the general form commonly used in rheostats and resistanceboxes having conducting blocks mounted on an insulating support, theseblocks being arranged as terminals of various elements of the circuitsand adapted to receive between them conical conducting plugs. The sidesof the blocks being drilled and rcaincd to form conical holes, theconical plugs serve to join the blocks together wherever inserted, andin the arrangement which 1 illustrate a wide variety of modificationsmay be made upon the circuits. The conducting blocks of the commutatorare indicated by the refcrence-lettcrs, c, (l, 0, f, g, h,'i, k, l, m,n, o, p and s. The conical plugs are omitted from the figure: They areof well known form and may be inserted into any of the holes between theblocks in order to bring about the desired circuit arrangements.v Theconica holes which may receive such plugs are indicated by thenumerals, 1. to 23, inclusive. The blocks are secured to a flatinsulating support, which latter is not shown in the drawings, and thebinding posts, 25, 26, l), 30 and Bi, the two keys formed respectivelyof the parts 27 and 28, and the parts 32, 33 and 34-, and thegalvanometer, G, are associated with said blocks, preferably by beingsecured to the same plate.

The zigzag lines, a, b, r and r, represent suitable resistances,adjustable between certain predetermined limits, in any suitable manner,as by the withdrawal or insertion of plugs in an ordinary plug rhcostat,by the moving of a pivoted arm over contact points having resistancesconnected between them, by the moving of a contact along a bareresistance wire, or in any other of the ways well known to the art ofelectrical testing. The resistance 1 must be adjustable to zero as oneof its limits. It is optional whether these ad justable resistances a,b, r and r be associated with the commutator as a unit. They may bemounted with equal accuracy of result in separate cases, althoughconnected to circuits of the commutator as indicated in Fig. 1. Thisoptional separation is also permissible in the case of the galvanomctcrand the keys.

The ofiice of'the commutator is to provide convenient methods ofswitching, by which the circuit relations required for the tests which Idescribe may be readily obtained. Scrutiny of the circuits in Fig. 1will make plain the considerable latitude of arrangement of parts thatmay be secured by inserting plugs in the variously numbered holes, thuselectrically joining the variously lettered blocks; it is not meant thatall of the plug holes shall be filled with plugs for a given test, orthat any tests are possible with all of the holes unplugged. As will befurther described, certain conditions of plugs will place the elementsinto certain required circuit arrangements.

Itis assumed at the outset that the various ordinary methods of testingfor the value of an unknown resistance by the Wheatstone bridgeprinciple are well known, and that that variation of the Wheatstonobridge principle which is known as the Varley loop test is also wellunderstood, as it is these methods which are by far the most widely usedin resistance measurements, particularly upon telegraph and telephonelines.

Considering the case of a test to be made to determine the location ofaground or cross upon one of two wires, one of the wires used in the testbeing clear of any fault, these two wires being joined at the distant Itbeing the resistance in ohms from the point of testing to the fault, f band a being the respective arms of the bridge in the general relationshown in the figure, L being the total series resistance of the twowires under test, or, in other words, of the loop, and r being theresistance of the rhcostat as varied to produce a' condition of nodeflection in the galvanometer.

The three distinct steps in the ordinary Varley loop test as performedon my apparatus may be understood by referring more particularly to theexact conditions shown in Fig.2. It is to be noted that the numeralsassociated with the drawing by small arrows have reference to theconnecting plugs in the commutator shown in Fig. 1.' For example, thenumeral 11 indicates that at the point referred to by its arrow the hole11 of the commutator is plugged up, thus producing the exact circuitcondition shown at that point in Fig. 2. Reference numerals, such as 30,shown adjacent to a point of the circuit but without the arrow indicateparts other than plug-hole parts of the commutator. Arranging thecommutator plugs as indicated, with a plug additionally in the hole 19,but with none in the hole 23, and adjusting the arms a and b to have aratio to each other of 1 to 10, of 1 to 100, or in any other ratio of lto some power of 10, the resistance r may be varied until no deflectionof the galvanometer G occurs when the keys having levers 27 and 32 aredepressed. Under the conditions established, the test made will havebeen a simple Wheatstone bridge measurement of the resistance of theloop L, and this resistance is determined at once by multiplying thedetermined resistance r by the previously established ratio of a to b.Knowing the value thus determined, unplugging the hole 19, plugging upthe hole 23 so as to apply the battery connection through the fault at fand E, the resistance r may be again adjusted to abalance. Allquantities in the second member of the Varley loop equation are nowknown, and the resistance R to the fault may thus be determined.

The foregoing illustrates the application of the commutator of myinvention totwo of the principal useful forms of testing involvingsubsequent calculations, that is, to the measurement of resistances, asof the loop L, Fig. 2, bythe simple Wheatstone bridge method, and to theordinary application of the bridge toVarley loop methods. 'By'means ofmy commutator or master switch I am enabled to perform many other of theordinary well known tests to which the Wheatstone bridge-is generallyadaptable. It is, however, to a new process or method of measurement orfault location, as well as to the arrangement of appa tus herein shown,that my invention is directed.

In the Varley loop test, as ordinarily practiced, three steps arenecessary: lirst,'the determination or the loop resistance of the twowires under test; second, the balancing of the good wire in series withthe reinotc portion of the" faulty wire against a known variableresistance in series with the near portion of the faulty wire, and,third, the substitution of the loop resistance determinedin the firststep, and the resistance necessary to balance as detcrminedin the secondstep, in the Varley loop equation already given, in order to solve fortheresistance to the fault on the faulty wire.

In my improved method, made possible by my improved arrangementofapparatus, the loop' resistance 'L 'is involved in the balancing of theresistance r,

and the resistance r then is retained as a part of the circuit ofthelater test. The introduction of the result of the first test into thesecond test thus is made automatically the necessity of any knowledge onthe part of the operator of the loop resistance or of the absolute valueof the r resistance is obviated. This method may now be understood byreferring to Fig. 3, bearing in mind the described meaning of referencenumerals accompanied by arrows. In addition to the inserted plugs asindicated in this figure, assume hole 23 to be plugged, hole 19 to beunplugged, and resistance r to be adjusted to zero; then the resistancer may be adjusted to a balance of the galvanometer under any of a largenumber of ratios between the bridge arms a and b: but for this ratio Inow choose values of a and b, such that a will be ]/9, 1/99, etc., of b,the sum of a and b being always, in the present illustration, some powerof ten when referred to a as a base. When a balance has been reached,unplug 23 and plug up 19, and once more manipulate the keys, and,leaving r as adjusted, adjust r until a balance has been reached. Thenthe resistance in ohms to the fault is the resistance r multiplied bythe ratio of the arm a to the sum of the arms a and b.. That this is sois readily proven: When hole 23 is plugged, grounding the battery, and abalance is secured by manipulating r, 1* being. zero,. L L

- -zmfi When hole 19 instead of 23 is plugged, and a balance againsecured, by manipulating r, leaving r as adjusted,

%E or Lanu 'g 2 Substituting this value for Lin (1) and solving for R,

But with the value chosen the sum of a and b is always some power of 10when referred to a as a base; there I and the cutane us simply to dividethe value a by the particular power of 10, or in other words to pointoff from the right of the adjusted'value of r as many places as thereare ciphers in the power, or units in the index of the power,

It will be seen that the operations here are exceedingly simple, andwith the prerequisite bridge arm relations established, no realcalculations whatever are necessary. It will be noticed that in thefirst adjustment. to galvanometer zero by the use of resistance r,something of the usual process of determining the value of theresistance r was accomplished, but. in erintrmlistinction from methodsrequiring an exact determination of the numerical value of theresistance r, my method takes no account of the. nominal runnericalvalue of r but only utilizes it in a way such that it final 1 ydisappears from the equation without its value having been definitelydetermined, leaving thatdetermination in the circuits as a means to afinal end, and not as an element of calculation. It will thus be seenthat the adjustable resistance denominated 'r may for this test ,be anyadjustable resistance but not necessarily a calibrated resistance: Allthat is re.- quired is that it be variable within reasonable limits, andthat it remain constant after adjustment only for the time required tocomplete the operations peculiar to the test.

Hometimcs it is desirable, as a check method, or for other reasons, tousea variable resistance in the limb of the line having no fault. Suchan arrangement is shown in Fig. 4, the. resistance r being placed in theopposite limb of the line from the resistance r. This arrangement isreadily accomplished with my commutator by inserting the plugs inthevarious proper holes as indicated by numerals in Fig. 4. With theapparatus thus arranged, the. test for the location of the fault, f, maybe made as follows: Plug up 23, unplug l9, and adjust r to zero.Establish a relation of bridge arms in which the sum of a and b is theproduct of b and some power of 10; adjust r to the balance of thegalvanometer. Now, unplug 23 and plug up 19, and make the arms a and bequal to each other-a ratio of unity- Then adjust r to a new balance ofthe galvanometer. The resistance to the fault is then the resistance. 1'divided ,by the ratio first established between 1) and the sum of a andb, or,

That this is so is thus proven; when the first balance was obtained,

' a W-L-R o t='" (2) When the. second balance was obtained with equalarms, then, rL=r. Substituting this in (2),

whence,

lint, under the values assumed for a and b,

It will be seen that the mathematical operations other than balancingare only with relation to the simple ratios of the bridge arms, and areaccomplished by pointing off or adding ciphers only.

Referring now to Fig. 5,- -39 is an adjustable resistance wire, rod, orsimilar uniform cornluetor; 37 and 38 are respectively contact. pointscapable of adjustable. contact with the resistance 39; 40 is ascaleassisting in determining the relation of the. resistance 3!) andthe contact points 37 and 38. .lty the adjustment. of 3b in contact with39, the total amount of resistance thus included in shunt with thegalvanometer (i may be arranged; by moving 37 with relation to 35), thetotal resistance included by 38 on 3!) may be divided into two parts,that. included between the contact points 37 and 38 corrcsponding to arma. in the previous figures, and the remaining portion corresponding tothe. arm I). With this arrangement and the process described withrelatir'm to Fig. 3, most rapid locations can be made. lly anarrangement of parts converting the positions of the. resistances 'r andr to be those shown in Fig. 4, the advantages of the slide wire bridgein Fig. 5 may be applied to the test described in connectionwith thatfigure also. in fact, if the slide wire shown in Fig. 5 be substitutedfor the resistances a. and f) of the other figures, any of the teststhat may be performed with my improved apparatus may be. accomplished,in many cases wth increased facility.

In the foregoing a most important. feature is that of the bridge-armratio, which by previous determination may eliminate all calculation ofthe resistance in ohms to the fault, which. is the result desired. It isnot. always necessary, however, to know the. resistance in ohms, as itis frequently important to know the distance in feet or meters, if theconductor be in a cable. In fact, the determination of tho reistanceto'the fault -is usually used as a basis of determining the distance tothe fault. My invention is 'apable of quite as convenient use toreaddirectly in terms of distance as in terms of resistance, and by theapplication of the same principles as I have already described.

Generally stated, the principle as applying to resistance determinationsis that one bridge arm shall be to the sum of the arms as l is to apower of 10.

In the case of results to be reached in terms of (listance, theprinciple may be stated as being that one bridge arm shall be to the sumof the arms as is to,

the length per ohm of the conductor under test. Thus, in the case offeet, as 1 is to the feet per ohm of the conductor, or in the case ofmiles, as 1 is to the miles per ohm of the conductor. To illustrate,suppose. a conductor having 63 feet per ohm were .under test: In makingthe Varley loop test as in Fig. 3, the arm (1. might be given a value ofunity and the arm I) a value of (32, equal to 63 1. Then the formulawhich finally expresses the result, becomes with these values,

in which R is the resistance in ohms to the fault. If now D be taken asthe distance in feet to the fault, it is evident that D 63R, whence itfollows that D=r. In other words, the adjusted value of the resistance ris equal to the distance in feet to the fault, and

the instrument thus used is direct reading. Were the conductor undertest of resistance of 63.2 it. per I 011m, the bridge might be set to 1and 62.2 respectively for the arms, or to 10 and 622 ohms, since ineither case the ratio is the same. v I l The quantity, feet per ohm,meters per ohm, etc., depends upon the specific resistance, the area ofcross sectiqn, and the temperature of the conductor and the conductormaterial, and can be determined by well known means, as from tables. Inthe case oi copper, for example, the resistance of a foot of circularwire, one-thousandth of an inch in diameter, may be said to be 108 ohms.If the cross section of a copper wire expressed in circular milsbedividod by 1.0.8 the result will be the number of feet per ohm of thewire.

A. foot of wire one-thousandth of an inch in diameter is called amil-foot; similarly, a mil-yard, mil-mile or mil'meter resistance may beemployed, the result of division being. in terms of yards per ohm, milesper olnn, meters per ohm, etc. Applying this matter to thesimplification of tests to be read in distance, I may adjust thebridgearms,-for example, in Fig. 3, so that arm a is to the sum of thearms a and b, as the mil foot of resistance of copper is to the area incircular mils of the wire under test. On balancing to a zero movement oftho galvanorneter by adjustment of the two resistances as described forthat figure, such a value of r is directly given as corresponds to thedistance in feet to the fault. For example, if the test were beingapplied to a faulty conductor in a cable formed of Wires of 22 Brown &Sharpe gage, the faulty conductor would be looped with any goodconductor at the distant end; the area of #22 wire in circular milsbeing 642.8, and the mil-foot resistance of copper being 10.8, thebridge would be respectively 10.8 for a and (642.8-10.8) or 032 ohms forb. The process of subtraction is rendered unnecessary in setting thebridge arms, as it is made automaticallyyby setting 37 to 10.8 and bysetting 88 to 642.8 the bridge arm b. becomes equal to the difference ofthe two values without the necessityof solving an equation for theactual value of the difference. Were the results desired to be in someother unit than feet, it would only be necessary to determine the propermil-unit amount for the arm a, placing-37 to that amount instead of to10.8in the above example. The results then would read directly intermsof the new lineal u'nit.

Variety is possible in the method of calibrating the scale. 'Two or morecalibrations may be used simultaneously. There. may be a scale forspecific resistgeneral work. The user now desiring to locate a fault ona circuit of 12 B. dz S. copper wire would set 37 to Copper and 38 to 12B. dz SJ and make the two adjustments of r and r, the letter of whichwould be a direct reading of the distance to the fault, in feet. A slidewire resistance is not an absolute necessity-in this system ofcalibrations, but it seems the simplest to show in the drawingsaccompanying these specifications.

Having thus described my invention, what I claim as new and desire tosecure by United States Letters Patent is,

1. In a Whentsiono bridge. the combination of a pair oi adjustableratio-arms, a current detector, an adjustable rcslstnnce adapted to formthe .iourflr arm of the bridge, a second adjustable and calibratedresistance adapted to be included in the fourth arm of the bridge andadopted to be adjustedindependently of said ilrsi: adjustableresistance, and a commutator adopted to connect together the elementsabove enumerated, a source of electric potential and the conductor undertest, substantially as described.

2. in an electrical testing'de'viee, the combination of a pair ofadjustable-ratio arms a current detector; an ad Justable resistance: asecond adjustable resistance adapted to be adjusted independently oisaid first adjustable re' sistancez-and a commutator having terminalsfor said parts and for a source oi. current and for a conductor to hetested, and adapted to connect said parts in a Whcuistone bridge systemwherein said pair of ratio arms form the first and second arms of thebridgesystem, sold ilrst adjustable resistance is included in a thirdarm and said socend adjustable resistance is included in the fourth urm,substantially as described.

3; in an electrical testing device, the combination ore pair ofadjustable ratio arms: a current detector; an ad Justable resistance; acommutator having terminals for said ports. for a conductor under test,and for a source of current; and a switch adopted to connect one of thecurrent-source terminals to a terminal of the conductor under test or toearth, alternatively, substantially as described.

4. In a Wheatstone bridge, a pair of adjustable ratio arms comprising acontinuous resistance extending from the extremity oi one arm throughthe point of current en trance to the. extremity of the other arm;adjusting means foradjusting the combined resistance of the said pair ofratio arms. and adjustable means for connecting the current source tosaid 'Joint arm-resistance whereby it may be connected at a pointdividing said joint arm-resistance into two arm-resistances torindividual bridge arms havinc' any desired ratio, substantially asdescribed.

5. In a Wheatstone bridge, a pair of adjustable ratio;

arms comprising a continuous slide-wire resistance; a

sliding contact: orfssid slide wire for adjusting the resist-f ance'o'tthe included portion of said slide wire; and a sec ond sliding contactfor. connecting the current source whereby it may be connected at apoint dividing the total included slide-wire resistaucointo tworesistances tonindivlduai bridge arms having any desired ratio,substanially as described.

-Signed by me at Portland, county oi! Multnomah and- State 0! Oregon, inthe presence oil-two witnesses, this ninth day of March, 1005., vHERBERT'M. FRIENDLY.

Witnesses: i

M. S. Farnnom', Anna 0. Rain.-

Corrections in Letters Patent No; 859,556.

It is hereby certified that Letters Patent No. 859,556, granted July 9,1997, upon the application of Herbert M. Friendly, of Portland, Oregon,for an improvement in.

Methods of and Apparatus for Fault Location on Electrical Conductors,errors.

appear in the printed specification requiring correction, as follows: Inline 70, page 1,

the word conica should read conical; line 49, page 3, in the equationr'L-R' should read r+L-R, and in line 52, page 3, r-L should read r'+Land that,

the said Letters Patent should be read with these corrections thereinthat the same may conform to the record of the case in the PatentOffice.

Signed and sealed this 3rd day of September, A. 1)., 1907.

E. B. MOORE,

, [SE-AL].

, Commissioner of Patents,

